Vacuum insulating glass unit with large pump-out port, and/or method of making the same

ABSTRACT

Certain example embodiments of this invention relate to vacuum insulating glass (VIG) units, and/or methods of making the same. More particularly, certain example embodiments relate to VIG units having large pump-out ports, and/or methods of making the same. In certain example embodiments, a vacuum insulating glass (VIG) unit is provided. First and second spaced-apart glass substrates are provided, and a gap is provided between the spaced-apart substrates. A pump-out port has a size (e.g., diameter) of at least about 30 mm. A cover seals the pump-out port. A getter is in communication with the gap. The pump-out port is sealed using the cover, in making the vacuum insulating glass unit, via a sealing material provided proximate to the cover and/or proximate to the pump-out port.

FIELD OF THE INVENTION

Certain example embodiments of this invention relate to vacuuminsulating glass (VIG) units, and/or methods of making the same. Moreparticularly, certain example embodiments relate to VIG units havinglarge pump-out ports, and/or methods of making the same. In certainexample embodiments, a vacuum insulating glass (VIG) unit is provided.First and second spaced-apart glass substrates are provided, and a gapis provided between the spaced-apart substrates. A pump-out port has adiameter of at least about 30 mm. A cover seals the pump-out port.Getter is in communication with the gap. The pump-out port is sealedusing the cover, in making the vacuum insulating glass unit, via asealing material provided proximate to the cover and/or proximate to thepump-out port.

BACKGROUND AND SUMMARY OF EXAMPLE EMBODIMENTS OF THE INVENTION

Vacuum IG units are known in the art. For example, see U.S. Pat. Nos.5,664,395, 5,657,607, and 5,902,652, the disclosures of which are allhereby incorporated herein by reference.

FIGS. 1-2 illustrate a conventional vacuum IG unit (vacuum IG unit orVIG unit). Vacuum IG unit 1 includes two spaced apart glass substrates 2and 3, which enclose an evacuated or low pressure space 6 therebetween.Glass sheets/substrates 2 and 3 are interconnected by peripheral or edgeseal of fused solder glass 4 and an array of support pillars or spacers5.

Pump out tube 8 is hermetically sealed by solder glass 9 to an apertureor hole 10 which passes from an interior surface of glass sheet 2 to thebottom of recess 11 in the exterior face of sheet 2. A vacuum isattached to pump out tube 8 so that the interior cavity betweensubstrates 2 and 3 can be evacuated to create a low pressure area orspace/gap 6. After evacuation, tube 8 is melted to seal the vacuum.Recess 11 retains sealed tube 8. Optionally, a chemical getter 12 may beincluded within gap 13.

A typical apparatus for pumping down and sealing of the VIG unit isdisclosed in U.S. Pat. No. 7,244,480, the entire contents of which areincorporated herein by reference. In the FIG. 3 embodiment of the '480patent, for example, while the whole VIG unit is in the atmosphere, theevacuation was accomplished through a pumping port tube using anupside-down cup connected to the vacuum system. Once the pump-down iscompleted, the pumping port is sealed by tipping off the tube using adevice, which can be either a wire heater, or focused IR source, or alaser, or other heating devices.

To achieve good insulating characteristics, the vacuum cavity must beunder vacuum, typically below about 1×10⁻⁴ torr. The vacuum is createdby means of vacuum pump removal of gasses between the edge-sealed platesof glass through a vacuum port or pump-out port. Typically, the pump outport includes a small diameter glass tube inserted into a pre-drilledhole in one of the glass plates, which is affixed and sealed using aperimeter ceramic frit, solder glass, and/or by other means. Once theappropriate vacuum level is reached within the vacuum gap, the glasstube is melted on the exposed end with a heat source, thereby sealingthe vacuum gap and maintaining the vacuum within the hermetically sealedglass plates. The time required to pump-down the VIG assembly torequired absolute pressure is a function of the pump out tube holediameter.

Conventionally, the hole has an outer diameter of less than about 5 mmand, typically, the hole outer diameter is only about 1-2 mm. The pumpout tube diameter must be small in order to quickly melt the end andallow the glass wall to collapse upon itself in order to seal the tube.Ultimate vacuum may not be reached if the pump out tube diameter is toosmall. However, if the tube is too large, there often are difficultiesassociated with focusing a laser on the tube to cause the meltingthereof.

Conventional sealing techniques, including laser-sealing techniques,disadvantageously trap radicals in the vacuum. For example, CO* radicalsmay be emitted from the carbonates in the glass into the vacuum. Thiscauses a pressure increase within the gap between substrates, resultingin a degradation in the insulating characteristics of the assembled VIGunit (e.g., a substantially instantaneous reduction in R-value). Largerholes tend to trap more radicals. This degradation occurs in addition tothe normal degradation caused when the VIG unit is exposed to UVradiation, as it is under normal conditions.

Thus, it will be appreciated that there is a need in the art forimproved VIG units, and/or methods of making the same, that overcome oneor more of these and/or other disadvantages. In addition, it also willbe appreciated that there is a need in the art for pump-out ports havingan increased diameter, improved vacuum and sealing techniques, and/ormethods for the same.

In certain example embodiments of this invention, a method of making avacuum insulating glass (VIG) window unit is provided. First and secondspaced-apart glass substrates are provided, a gap being provided betweenthe spaced-apart substrates. A pump-out port has a size (e.g., diameter)of at least about 30 mm. A cover for use in sealing the pump-out port isprovided. Getter is in communication with the gap. The pump-out port issealed using the cover, in making the vacuum insulating glass unit, viaa sealing material provided proximate to the cover and/or proximate tothe pump-out port.

In certain example embodiments, a vacuum insulating glass (VIG) unit isprovided. First and second spaced-apart glass substrates are provided,and a gap is provided between the spaced-apart substrates. A pump-outport has a diameter of at least about 30 mm. A cover seals the pump-outport. Getter is in communication with the gap. The pump-out port issealed using the cover, in making the vacuum insulating glass unit, viaa sealing material provided proximate to the cover and/or proximate tothe pump-out port.

The features, aspects, advantages, and example embodiments describedherein may be combined to realize yet further embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages may be better and morecompletely understood by reference to the following detailed descriptionof exemplary illustrative embodiments in conjunction with the drawings,of which:

FIG. 1 is a prior art cross-sectional view of a conventional vacuum IGunit;

FIG. 2 is a prior art top plan view of the bottom substrate, edge seal,and spacers of the FIG. 1 vacuum IG unit taken along the section lineillustrated in FIG. 1;

FIG. 3 is an illustrative side view of a glass bung inserted into a bunghole of a substrate in accordance with an example embodiment;

FIG. 4 is a more detailed side view of a bung hole in accordance with anexample embodiment;

FIG. 5 is an illustrative bung including getter material in accordancewith an example embodiment;

FIG. 6 is an illustrative bung including a getter cell attached to abottom surface thereof, in accordance with an example embodiment;

FIG. 7 is a VIG assembly including a getter cell and a bung inaccordance with an example embodiment;

FIG. 8 is an illustrative side view of molten glass inserted into a holeof a substrate in accordance with an example embodiment;

FIG. 9 is an illustrative side view of a metal disc covering a hole of asubstrate in accordance with an example embodiment; and

FIG. 10 is another illustrative side view of a metal disc covering ahole of a substrate in accordance with an example embodiment.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Certain embodiments of this invention relate to an improved peripheralor edge seal in a vacuum IG window unit, and/or a method of making thesame. “Peripheral” and “edge” seals herein do not mean that the sealsare located at the absolute periphery or edge of the unit, but insteadmean that the seal is at least partially located at or near (e.g.,within about two inches) an edge of at least one substrate of the unit.Likewise, “edge” as used herein is not limited to the absolute edge of aglass substrate but also may include an area at or near (e.g., withinabout two inches) of an absolute edge of the substrate(s). Also, it willbe appreciated that as used herein the term “VIG assembly” refers to anintermediate product prior to at least the evacuation of the gapincluding, for example, two parallel-spaced apart substrates. Also,while a component may be said to be “on” or “supported” by one or moreof the substrates herein, this does not mean that the component mustdirectly contact the substrate(s). In other words, the word “on” coversboth directly and indirectly on, so that the component may be considered“on” a substrate even if other material (e.g., a coating and/or thinfilm) is provided between the substrate and the component.

In certain example embodiments of this invention, a vacuum insulatingglass (VIG) unit and/or method of making the same is provided. First andsecond spaced-apart glass substrates are provided, and a gap is providedbetween the spaced-apart substrates. A pump-out port has a size (e.g.,diameter) of at least about 30 mm. The word “size” as used herein meansdiameter, width or other distance across the port, preferably at itswidest location. A cover seals the pump-out port. Getter is incommunication with the gap. The pump-out port is sealed using the cover,in making the vacuum insulating glass unit, via a sealing materialprovided proximate to the cover and/or proximate to the pump-out port.

Increasing the pumping port open area has several associated advantages.For example, a larger area allows for faster pump-down to the ultimatevacuum level desired with a given vacuum pumping system. Also, a largerarea may facilitate a lower ultimate vacuum level, which means betterinsulating properties for the VIG unit. Additionally, novel designs mayallow getter material to be incorporated through the port as a part ofthe vacuum port plug, a sealing device, and/or as a stand alone cell.Getter materials advantageously may be incorporated into VIG units toremove traces of gas from sealed evacuated systems. Still further,aesthetic features may be incorporated into a sealing device, e.g., abung may be laser-etched or sandblasted with a logo, trademark, and/ormay incorporate other markings. The port may be designed to beself-sealing, by means of the cavity vacuum, pulling the closing devicetighter to create an improved gas seal.

A first example design technique relates to the inclusion of a bungstyle port, which will now be described in connection with FIGS. 3-7.FIG. 3 is an illustrative side view of a glass bung 32 inserted into abung hole 40 of a substrate 30 in accordance with an example embodiment.In FIG. 3, a pre-manufactured glass bung 32 is used. The glass bung 32includes a tapered shape that mates to a pre-drilled tapered hole 40formed in one of the glass substrates 30. In particular, the bung 32 istapered such that it is wider towards the exterior surface of the bung32 and narrows towards the gap between substrates. The taper is betweenabout 5 degrees and 50 degrees from vertical, and more preferablybetween about 10 degrees and about 35 degrees from vertical, such thatthe bung 32 will seal tightly to the mating pre-drilled hole 40 in thesubstrate 30. The bung 32 is designed so that it is substantially flushwith (e.g., only slightly raised above) the outer surface of thesubstrate 30. The top surface of the bung 32 may include an aestheticfeature such as, for example, a laser-etched or sandblasted emblem,logo, and/or other design. Preferably, the bung size (e.g., diameter) atits smallest or largest location is greater than about 30 mm, morepreferably greater than about 40 mm, and still more preferably greaterthan about 50 mm.

FIG. 4 is a more detailed side view of a bung hole 40 in accordance withan example embodiment. The taper of the hole 40 corresponds to the taperangle of the bung 32. Preferably, the main taper of the hole 40 differfrom the taper angle of the bung 32 by no more than about 5 degrees,more preferably by no more than about 3 degrees, and still morepreferably by no more than about 2 degrees. In certain exampleembodiments, the tapered hole may include chamfered edges 42, 44proximate to the outer and inner surfaces of the substrate 30,respectively. The chamfered edges 42, 44 may help reduce the likelihoodof breakage caused by edge imperfections. The hole 40 may be made withany suitable technique such as, for example, with a 1- or 2-sided drill,with water jet equipment, and/or the like. Additionally, a grindingoperation may be performed on the tapered hole 40 (e.g., after it isinitially formed), for example, to smooth the surface of the hole 40 andthereby reduce imperfections that could cause breakage.

Getter material may be applied to the bung and/or to one or both taperededges of the bung hole 40. For example, FIG. 5 is an illustrative bung50 including getter material 54 in accordance with an exampleembodiment. A recess or channel 52 is formed in the bung 50. The edgesof the recess may have getter material 54 applied thereto.

Additionally, or in the alternative, a bung may have a getter cellconnected thereto. For example, FIG. 6 is an illustrative bung 60including a getter cell 62 attached to a bottom surface thereof, inaccordance with an example embodiment. The getter cell 62 including thegetter material 54 may be activated once the VIG unit is sealed. Incertain example embodiments, the getter cell 62 may be a stand-alonecomponent. In certain example implementations, the getter cell 62 may besubstantially cylindrically shaped. The outer size (e.g., diameter) ofthe cell 62 may be slightly smaller than the small end of the taperedhole 40 so that it may be placed inside the VIG assembly prior to finalsealing.

FIG. 7 is a VIG assembly including a getter cell 62 and a bung 32 inaccordance with an example embodiment. As shown in FIG. 7, the gettercell 62 may sometimes be slightly taller than the gap between the panesof glass 2, 3. The bung 32 may be sized such that it does not touch thegetter cell 62 once in place and sealed. The getter cell may be loose,or free floating, within the gap between the substrates 2, 3. Also, thegetter cell 62 may be designed with a perimeter ring of small standoffsto reduce the amount of direct contact with the bottom glass substrate3. Additionally or in the alternative, the getter and/or the getter cellmay be slightly curved at the bottom to reduce contact points.Additionally or in the alternative, the getter and/or the getter cellmay be slightly curved at the bottom to reduce contact points.

Referring once again to FIG. 3, the bung 32 may be sealed (e.g., to thesubstrate 30) using any suitable means. For example, a frit 34 that isfired may help to seal the vacuum port. In a first exampleimplementation, the frit 34 may be applied at a prescribed thickness tothe sealing surfaces of the hole 40 and/or the bung 32, and also may bepre-fired prior to a vacuum process step. Once a desirable vacuum levelis achieved, the bung 32 and surrounding glass may be heated to themelting point of frit 34, e.g., using a localized heat source such as,for example, focused infrared, microwave, laser, and/or heat sources, tore-melt the frit and bond the bung to the glass panel and hermeticallyseal the VIG unit.

In a second example implementation, the frit 34 may be appliedexternally, e.g., as a paste around the perimeter of the bung 32. Thearea may be heated, e.g., using a localized heat source to melt the frit34 and create the seal. In a third example implementation, a localizedheat source with focused heating may be used to melt the glass betweenthe bung 32 and the glass panel 30. In a fourth example implementation,the bung 32 may be coated to a specific thickness with a metal, such asIndium, which may act as a solder between the bung 32 and glass panel 30surfaces when melted using a focused heat source. It will be appreciatedthat these bung-sealing techniques may be used alone or in variouscombinations.

A second example design technique relates to the inclusion of a moltenglass seal, which will now be described in connection with FIG. 8, whichis an illustrative side view of molten glass 60 inserted into a hole ofa substrate 2 in accordance with an example embodiment. A defined volumeof molten glass 60 is metered from a heated tube into the hole of theglass substrate 2. The hole may be sized according to the exampledimensions provided above or in some other way. The hole may be taperedas described above, or it may be substantially straight. Once the moltenglass volume is dispensed, the molten glass is tamped to bring it levelor slightly above level with the top surface of the glass substrate 2. Atamping device is brought into contact with the molten glass 60 andpushes it further into the hole. The tamping device may contain anemblem or logo or other marking to create an imprint or other aestheticfeature in the molten glass surface.

The molten glass may be suspended above the bottom glass panel by meansof a getter cell 62, or by other mechanical means so as to reduce theamount of direct contact with the bottom substrate 3, which otherwisemay impair thermal insulation effect. Getter material 54 may beincorporated into such a design. The getter cell 62 may be designed,sized, positioned, etc., in the above-described and/or other ways.

As described above, the hole may have straight or tapered sides and alsomay incorporate chamfered edges, e.g., to reduce the likelihood ofthermal stress and/or breakage caused by edge imperfections. The holemay be formed and/or finished using the above-described and/or othertechniques.

A third example design technique relates to the inclusion of a metaldisc seal, which will now be described in connection with FIGS. 9-10.FIG. 9 is an illustrative side view of a metal disc 90 covering a holeof a substrate 30 in accordance with an example embodiment, and FIG. 10is another illustrative side view of a metal disc 90 covering a hole ofa substrate 2 in accordance with an example embodiment.

In both FIGS. 9 and 10, a pre-manufactured metal disc 90 is utilized toseal the pump-out hole. The metal disc 90 optionally may be a stampedshape that mates with a pre-drilled hole (e.g., in the substrate 30 inFIG. 9 and the substrate 2 in FIG. 10). The “metal strip” may be made ofone metal or a plurality of metals (metal alloy), and may include smallamounts of non-metals such as oxygen or the like, and also may coatedwith a non-metal. The metal chosen may have approximately the samecoefficient of thermal expansion as that of the glass substrates. Thecoefficient of thermal expansion is a thermodynamic property of asubstance that relates the change in temperature to the change in amaterial's dimensions. The coefficient of thermal expansion for sodalime glass is about 8.5×10⁻⁶/K at room temperature. Preferably, thecoefficient of thermal expansion between the metal and the glass vary bynot more than about 30%, more preferably by not more than about 25%, andstill more preferably by not more than about 15%. In certain exampleembodiments, the difference between the coefficients of thermalexpansion may be measured over (e.g., compared or averaged over) atemperature range of interest, which may be from about −40° C. to about50° C. in certain example implementations. Thus, the metal may besomewhat flexible.

In certain example embodiments, the metal itself may be resistant toatmospheric oxidation, as it may be exposed to atmospheric conditions.Additionally, or in the alternative, a metallic and/or other coating maybe applied to at least a portion of the strip (e.g., the entire strip,the outwardly exposed portions of the strip, etc.) to reduce the impactof atmospheric oxidation. Such an oxidation-reducing coating may be ofany suitable metal, or alternatively may be of silicon nitride or thelike in example embodiments.

As shown in FIG. 9, the bottom surface of the metal disc 90 mayincorporate a getter material 54, or another material that has a reducedsusceptibility to outgassing and/or oxidation. The metal disc 90 willcover a hole sized according to the example dimensions provided above orin some other dimensions. The metal disc 90, may be substantially flator it may be a stamped disc that includes a depression, the depressioncovering at least a portion of the hole. With respect to the latterdesign arrangement, FIGS. 9 and 10, for example, show a metal disc 90including a depression formed approximately in the center thereof. Thedepression covers most of the hole, and two feet extend from either sideof the depression so as to be on, directly or indirectly, the outersurface of the glass substrate, e.g., to provide stability and/or tohelp more fixedly attach the metal disc 90 to the appropriate substrate.The top surface of the plate may contain a stamped, laser etched orsandblasted, and/or otherwise provided emblem, logo, or other aestheticfeature.

The metal disc 90 related arrangements also may incorporate getter. Forexample, as shown in FIG. 9, the metal disc 90 may incorporate thegetter 54 as a surface application on the bottom side thereof (e.g., theside closest to the substrate). A protective metal film 92 mayencapsulate the getter until it is ready for use (e.g., until the metaldisc 90 has been placed on and/or fixed to the substrate 30, after avacuum is created in the gap between the substrates, etc.).

In certain example arrangements, a getter cell may be attached to abottom surface of the metal disc 90. The getter cell including thegetter material 54 may be activated once the VIG unit is sealed. Incertain example embodiments, the getter cell may be a stand-alonecomponent. In certain example implementations, the getter cell may besubstantially cylindrically shaped. The outer size (e.g., diameter) ofthe cell may be slightly smaller than the small end of the tapered holeso that it may be placed inside the VIG assembly prior to final sealing.

As shown in FIG. 10, the getter cell 62 may sometimes be slightly tallerthan the gap between the panes of glass 2, 3. The metal strip 90 may beformed such that it does not touch the getter cell 62 once in place andsealed (e.g., a depression of the metal disc 90 does not contact thegetter cell 62). The getter cell may be loose, or free floating, withinthe gap between the substrates 2, 3. Also, the getter cell 62 may bedesigned with a perimeter ring of small standoffs to reduce the amountof direct contact with the bottom glass substrate 3. Additionally or inthe alternative, the getter and/or the getter cell may be slightlycurved at the bottom to reduce contact points.

As described above, the hole may have straight or tapered sides and alsomay incorporate chamfered edges, e.g., to reduce the likelihood ofthermal stress and/or breakage caused by edge imperfections. The holemay be formed and/or finished using the above-described and/or othertechniques.

The metal disc 90 may be sealed to a substrate in any suitable fashion.For example, certain example embodiments may incorporate a sealingmaterial or compound 34 (described in greater detail below) that isfired or melted to seal the vacuum port. In a first example sealingtechnique, ceramic frit is applied as an ink to the sealing surfaces ofthe hole and the metal disc and is pre-fired (e.g., melted and allowedto cool and harden) prior to vacuum process step. During the vacuumpump-out process, once vacuum level is achieved, the disc andsurrounding glass is heated to the melting point of frit. This may beaccomplished using localized heating from a localized heat source suchas, for example, a focused infrared (IR), microwave, laser, and/or otherlocalized heat source, to re-melt the frit and bond the disc to theglass panel.

In a second example sealing technique, frit is applied externally as apaste around the perimeter of the metal disc. The frit is then heated tothe melting point using a localized heat source to melt the frit andcreate a permanent seal. In a third example sealing technique, the discis coated to a specific thickness of a glass solder metal, such asIndium, which acts as a solder between the disc and glass panelsurfaces, and is melted using a focused heat source and then allowed tocool.

It will be appreciated that such example sealing techniques may be usedalone or in various combinations. Also, it will be appreciated that anysuitable sealing material may be used (e.g., a metal frit of lead,silver, Indium; a ceramic or glass frit; and/or the like) in connectionwith certain example embodiments. Also, it will be appreciated that suchsealing materials may be applied to at least a portion of the metal disc(e.g., proximate to where the metal disc will contact, directly orindirectly, the substrate, etc.) and/or to the substrate proximate towhere it will contact, directly, or indirectly, the metal strip. Afrit-to-frit bond may advantageously promote the bonding in certainexample embodiments. Optionally, sealing material may be placed over thecover (e.g., directly or indirectly on the bung, glass, or metal disc)after it is at least initially placed on or sealed to the substrate.

It will be appreciated that the vacuum applied to the assembly will“pull” the particular cover implemented further and further “into” thegap in the substrate, thereby forming a good seal. Optionally, the cover(e.g., the bung, glass, or metal disc) may be preheated, e.g., to reducecracks from forming in the cover and/or the sealing material. Theheating may be close to the melting point of glass (which generally isfrom about 400° C.-600° C., and is about 580° C. for soda lime glass,depending on the composition of the glass).

In certain example embodiments, the large pump-out port is providedproximate to a corner of the VIG assembly. However, it will beappreciated that the pump-out hole of certain example embodiments may beformed in various locations, including locations on either the first orsecond substrate, or in edge seal of the VIG unit (which typically ismade of a frit). Also, the getter material used in connection withcertain example embodiments described herein may be any suitable getter,such as, for example, a getter material commercially available fromSAES. The getter material may include, for example, barium, aluminum,magnesium, calcium, sodium, strontium, cesium, and/or phosphorus. Thegetter material may be “activated” as described above in any suitablemanner. For example, heat may be focused onto the cell or film encasingthe getter material, e.g., to burn a hole therein or otherwise exposethe getter.

In certain example embodiments, the amount of getter included in theassembly may be sufficient to reduce the amount of outgassingexperienced by conventional VIG units to thereby maintain the gapbetween the substrates at or close to its desired vacuum pressure, e.g.,over the life of the VIG unit (typically defined by a warranty period).Thus, the insulating characteristics of the VIG unit (e.g., as measuredby the R-value of the VIG unit) also may be may be maintained over thisperiod.

It will be appreciated that the example embodiments described herein maybe used in connection with a variety of different VIG assembly and/orother units or components. For example, the substrates may be glasssubstrates, heat strengthened substrates, tempered substrates, etc.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

What is claimed is:
 1. A method of making a vacuum insulating glass(VIG) window unit, the method comprising: providing first and secondspaced-apart glass substrates, a gap being provided between thespaced-apart glass substrates; providing a pump-out port in one of theglass substrates, the pump-out port having a size of at least about 30mm; providing a cover for use in sealing the pump-out port; providing agetter in communication with the gap; sealing the pump-out port usingthe cover, in making the vacuum insulating glass unit, via a sealingmaterial provided proximate to the cover and/or the pump-out port. 2.The method of claim 1, further comprising applying the getter to atleast a portion of the cover.
 3. The method of claim 1, furtherproviding a getter-inclusive cell located in the gap between thesubstrates.
 4. The method of claim 1, wherein the pump-out port has adiameter of at least about 50 mm.
 5. The method of claim 1, furthercomprising tapering the pump-out port to an angle of from about 10degrees to about 35 degrees from vertical, the pump-out port beingnarrowest proximate to the gap between the substrates.
 6. The method ofclaim 1, further comprising chamfering one or more edges of the pump-outport.
 7. The method of claim 1, wherein the cover comprises a glassbung.
 8. The method of claim 7, further comprising tapering the pump-outport to an angle of from about 10 degrees to about 35 degrees fromvertical, the pump-out port being narrowest proximate to the gap betweenthe substrates, and wherein the glass bung is tapered to an anglediffering from the angle of the pump-out port by no more than about 5degrees.
 9. The method of claim 7, further comprising forming a recessin the glass bung such that the recess opens into the gap between thesubstrates; and applying a getter to the glass bung proximate to therecess.
 10. The method of claim 1, further comprising at least initiallyproviding the cover as molten glass; and tamping the molten glass intoplace such that, when hardened, the glass does not contact both thefirst and second substrates.
 11. The method of claim 1, wherein thecover comprises a metal disc.
 12. The method of claim 11, wherein themetal disc includes a depression at least partially insertable into thepump-out port.
 13. The method of claim 1, further comprising preheatingthe cover to facilitate the sealing of the pump-out port.
 14. The methodof claim 1, further comprising: applying the sealing material to thefirst and/or second substrates proximate to the pump-out port, and/or tothe cover at one or more glass-to-edge-sealing surfaces thereof; andbonding the at least one cover to the first and/or second substratesproximate to the pump-out port by heating and cooling, in this order,and wherein the sealing material is at least partially melted duringheating of the substrates and the cover.
 15. The method of claim 14,further providing localized heat at least proximate to the pump-out portin order to cause the at least partial melting of the sealing material.16. The method of claim 14, further comprising providing the sealingmaterial over the cover and/or to an area proximate to the sealedpump-out port.
 17. The method of claim 1, further comprising evacuatingan area between the first and second substrates to a pressure less thanatmospheric in making the VIG unit.